A combination service is a service for simultaneously performing two or more services between first and second users. Also, the combination service is a service for simultaneously performing two or more services between first and second users. Also, the combination service can be a service for combining at least two or more services among a first service based on a first network, a second service based on a second network and a third service based on a third network between the first and second users, and simultaneously performing them.
In order to perform the combination service between the first and second users, the first and second users should recognize information on a service, etc., that can be supported by each other and negotiate services available therebetween.
Herein, a CSI (Combination of CS and IMS services) will be explained as an example of the combination service.
The CSI is a service for combining a CS (Circuit Switched) service and an IMS (IP Multimedia Subsystem) service and simultaneously performing them between the first and second users. An IMS session for the IMS service can be added to a CS call established between the first and second users, or conversely, the CS call can be added to the IMS session established between the first and second users. The IMS service that can be added to the CS call which has been already established between the first and second users may include IMS-based services such as an instant messaging (IM), video sharing, a data delivery, etc.
FIG. 1 shows a network configuration for providing a general combination service, for example, a CSI, between the first and second terminals. As shown in FIG. 1, the network for providing the general combination service, e.g., the CSI, includes first and second CS core networks 31 and 32 for supporting a CS service for the CSI between the first and second terminals 10 and 20; first and second IMS core networks 41 and 42 for supporting an IMS service for the CSI to the first and second terminals 10 and 20; a first application server (AS) 43 connected with the first IMS core network 41 and performing a particular function of the IMS session of the CSI, e.g., a service-based charging function, of the IMS session of the CSI of the first terminal 10; a second server 44 connected with the second IMS core network 42 and performing a particular function (E.G., a service-based charging function) of the IMS session of the CSI of the second terminal 20; a radio access network (xRAN) 30 for connecting the first terminal 10 to the first CS core network 31 and the first IMS core network 41; and a second radio access network (xRAN) 33 for connecting the second terminal 20 to the second CS core network 32 and the second IMS core network 42.
The network for providing the CSI additionally includes a first PS (Packet Switched) core network 40 connected between the first xRAN 30 and the first IMS core network 41 to establish an IMS session of the CSI; and a second PS core network 45 connected between the second x-RAN 30 and the second IMS core network 42 to establish the IMS session of the CSI.
The first and second CS core networks 31 and 32 include an MSC (Mobile Switching Center), a VLR (Visiting Location Register) and an HLR (home Location Register), respectively.
The general CSI providing method in the general network for providing the CSI will now be described.
In case of the CS call between the first and second terminals 10 and 20, data and a control signal are exchanged through the first and second core networks 31 and 32, and in case of the IMS session, data and a control signal are exchanged through the first PS core network 40, the first IMS core network 41, the second IMS core network 42 and the second PS core network 45.
The first terminal 10 includes a function for being simultaneously connected to the first CS core network 31 and the first PS core network 40, and the second terminal 20 includes a function for being simultaneously connected to the second CS core network 32 and the second PS core network 45.
Before the CSI service starts between the first and second terminals 10 and 20, the first and second terminals 10 and 20 exchange their radio environment information of the current terminals and terminal capability information to recognize information about services that can be supported by each other.
The current radio environment information of the terminals 10 and 20 is used as important information for a user to determine a behavior after the CS call is established. Namely, the user can determine whether to exchange the terminal capability information or start the IMS session according to the current radio environment information.
The radio environment information is exchanged through a CS domain while the CS call is being established. The radio environment information is flexible and may differ according to an environment when the CS call is established, so the exchanged radio environment information is used as valid information only during duration of the CS call.
The radio environment information includes information indicating whether the terminals support the simultaneous using of the CS service and the PS service, etc. The terminal capability information is exchanged through an IMS domain.
FIG. 2 shows a general method for exchanging the terminal capability information between the first and second terminals.
In order to request the capability information of the second terminal, the first terminal 10 transmits an SIP (Session Initiation Protocol) OPTIONS message to the second terminal 20 (step S1). Then, the second terminal 20 stores address information of the first terminal 10 included in the SIP OPTIONS message (step S2) and transmits a 200 OK message in response to the SIP OPTIONS message. The 200 OK message includes the capability information of the second terminal 20 (step S3).
Upon receiving the 200 OK message, the first terminal 10 stores the capability information of the second terminal 20 included in the 200 OK message (step S4).
Meanwhile, after receiving the SIP OPTIONS message from the first terminal 10, if the second terminal 20 has not transmitted SIP OPTIONS message for requesting terminal capability information to the first terminal 10, the second terminal 20 determines to transmit the SIP OPTIONS message to the first terminal 10 to request the capability information of the first terminal 10 (step S5). When the SIP OPTIONS message that requests the capability information of the first terminal 10 is received from the second terminal 20, the first terminal 10 stores address information of the second terminal 20 included in the SIP OPTIONS message (step S7) and transmits a 200 OK message as a response message to the second terminal 20 (step S8). The 200 OK message includes the capability information of the first terminal 10.
The second terminal 20 stores the capability information of the first terminal 10 included in the 200 OK message transmitted from the first terminal 10 (step S9).
In this manner, the capability information of the first and second terminals 10 and 20 exchanged between the first and second terminals are stored in the first and second terminals 10 and 20 to quickly set a service and reduce a network load for communications later.
Accordingly, in order for a particular terminal to obtain capability information of the other terminal, it should transmit the SIP OPTIONS message for requesting terminal capability information to the other terminal and receive a response message including capability information of capability information of the other terminal from the other terminal.
The general terminal capability information exchanging method in the CSI providing network, respective terminals transmit the SIP OPTIONS message to the other terminal to obtain the capability information of the other terminal and store them.
Meanwhile, in a state the first and second terminals have performed the combination service, recognize terminal capability information of mutually other terminals and store them in respective caches, when the first and second terminal want to perform the combination service, namely, the CSI, again, the first and second terminals establish the IMS session for the CSI. And then, the first and second terminals check that the terminal capability information of the other terminal has been stored in a local area, namely, in the cache, and perform an INVITE message transmission procedure for an IMS session connection, without performing the terminal capability information exchange procedure.
In this case, if the terminal capability information of at least one of the first and second terminals has been updated, the terminal capability information stored in the cache of respective terminals and the actual terminal capability information are not the same, the IMS session connection by the INVITE message would be failed. Thus, as the IMS session connection is failed, the first and second terminal perform the capability exchange procedure and then perform the INVITE message transmission/reception procedure for the IMS session connection.
Therefore, the general terminal capability information exchanging method has the following problem.
That is, even when the terminal capability information stored in the cache of each terminal is different from the actual terminal capability information, the IMS session connection procedure is performed by using the INVITE message based on the terminal capability information of the other terminal stored in their cache. Thus, the performing of the unnecessary INVITE message transmission/reception procedure causes a waste of the network signaling and network resources.
In addition, even when only the terminal capability information of one terminal is changed, not that the terminal capability information of both terminals are not changed, the terminal capability information are exchanged between both terminals.
That is, in the general terminal capability information exchanging method, when the terminal capability information of the first terminal is changed while that of the second terminal is not changed, the first terminal transmits the SIP OPTIONS MESSAGE to the second terminal to receive the terminal capability information of the second terminal, and the second terminal transmits the SIP OPTIONS message to the first terminal to receive the terminal capability information of the first terminal. Thus, the unnecessary procedure, namely, the procedure of requesting and obtaining the terminal capability information of the other terminal which has not been changed, is performed disadvantageously.
Because the unnecessary procedure is performed, the network signaling and network resources are wasted.
Also, there is no way for the particular terminal whose terminal capability information has been changed to inform the other terminal that the change in its terminal capability information.